Add links to playground for several fixes

Author: TobiasNx

README.md

@@ -170,6 +170,8 @@ Does nothing. It is used for benchmarking in Catmandu.
 nothing()
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=nothing)
+
 ##### `put_filemap`
 
 Defines an external map for [lookup](#lookup) from a file or a URL. Maps with more than 2 columns are supported but are reduced to a defined key and a value column.
@@ -178,6 +180,8 @@ Defines an external map for [lookup](#lookup) from a file or a URL. Maps with mo
 put_filemap("<sourceFile>", "<mapName>", sep_char: "\t")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=put_filemap)
+
 The separator (`sep_char`) will vary depending on the source file, e.g.:
 
 | Type | Separator  |
@@ -207,6 +211,8 @@ put_map("<mapName>",
 )
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=put_map)
+
 ##### `put_rdfmap`
 
 Defines an external RDF map for lookup from a file or an HTTP(S) resource.
@@ -218,6 +224,8 @@ put_rdfmap("<rdfResource>", "<rdfMapName>", target: "<rdfProperty>")
 put_rdfmap("<rdfResource>", "<rdfMapName>", target: "<rdfProperty>", select_language: "<rdfLanguageTag>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=put_rdfmap)
+
 ##### `put_var`
 
 Defines a single global variable that can be referenced with `$[<variableName>]`.
@@ -226,6 +234,8 @@ Defines a single global variable that can be referenced with `$[<variableName>]`
 put_var("<variableName>", "<variableValue>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=put_var)
+
 ##### `put_vars`
 
 Defines multiple global variables that can be referenced with `$[<variableName>]`.
@@ -237,6 +247,8 @@ put_vars(
 )
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=put_vars)
+
 #### Record-level functions
 
 ##### `add_field`
@@ -247,6 +259,8 @@ Creates a field with a defined value.
 add_field("<targetFieldName>", "<fieldValue>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=add+field)
+
 ##### `array`
 
 Converts a hash/object into an array.
@@ -281,6 +295,8 @@ end
 call_macro("<macroName>"[, <dynamicLocalVariables>...])
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=call+macro)
+
 ##### `copy_field`
 
 Copies a field from an existing field.
@@ -289,6 +305,9 @@ Copies a field from an existing field.
 copy_field("<sourceField>", "<targetField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=copy+field)
+
+
 ##### `format`
 
 Replaces the value with a formatted (`sprintf`-like) version.
@@ -321,6 +340,9 @@ Moves a field from an existing field. Can be used to rename a field.
 move_field("<sourceField>", "<targetField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=move+field)
+
+
 ##### `parse_text`
 
 Parses a text into an array or hash of values.
@@ -352,6 +374,8 @@ paste("my.string", "~Hi", "a", "~how are you?")
 # "my.string": "Hi eeny how are you?"
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=paste)
+
 ##### `print_record`
 
 Prints the current record as JSON either to standard output or to a file.
@@ -401,6 +425,8 @@ Removes a field.
 remove_field("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=remove+field)
+
 ##### `rename`
 
 Replaces a regular expression pattern in subfield names of a field. Does not change the name of the source field itself.
@@ -409,6 +435,8 @@ Replaces a regular expression pattern in subfield names of a field. Does not cha
 rename("<sourceField>", "<regexp>", "<replacement>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=rename)
+
 ##### `retain`
 
 Deletes all fields except the ones listed (incl. subfields).
@@ -417,6 +445,8 @@ Deletes all fields except the ones listed (incl. subfields).
 retain("<sourceField_1>"[, ...])
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=retain)
+
 ##### `set_array`
 
 Creates a new array (with optional values).
@@ -426,6 +456,8 @@ set_array("<targetFieldName>")
 set_array("<targetFieldName>", "<value_1>"[, ...])
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=set+array)
+
 ##### `set_field`
 
 Creates (or replaces) a field with a defined value.
@@ -465,6 +497,8 @@ Deletes empty fields, arrays and objects.
 vacuum()
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=vacuum)
+
 #### Field-level functions
 
 ##### `append`
@@ -475,6 +509,8 @@ Adds a string at the end of a field value.
 append("<sourceField>", "<appendString>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=append)
+
 ##### `capitalize`
 
 Upcases the first character in a field value.
@@ -483,6 +519,8 @@ Upcases the first character in a field value.
 capitalize("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=capitalize)
+
 ##### `count`
 
 Counts the number of elements in an array or a hash and replaces the field value with this number.
@@ -499,6 +537,8 @@ Downcases all characters in a field value.
 downcase("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=downcase)
+
 ##### `filter`
 
 Only keeps field values that match the regular expression pattern. Works only with array of strings/repeated fields.
@@ -515,6 +555,8 @@ Flattens a nested array field.
 flatten("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=flatten)
+
 ##### `from_json`
 
 Replaces the string with its JSON deserialization.
@@ -549,6 +591,8 @@ Options:
 isbn("<sourceField>"[, to: "<isbnFormat>"][, verify_check_digit: "<boolean>"][, error_string: "<errorValue>"])
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=isbn)
+
 ##### `join_field`
 
 Joins an array of strings into a single string.
@@ -557,6 +601,8 @@ Joins an array of strings into a single string.
 join_field("<sourceField>", "<separator>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=join+field)
+
 ##### `lookup`
 
 Looks up matching values in a map and replaces the field value with this match. [External files](#put_filemap), [internal maps](#put_map) as well as [RDF resources](#put_rdfmap) can be used.
@@ -624,6 +670,8 @@ Adds a string at the beginning of a field value.
 prepend("<sourceField>", "<prependString>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=prepend)
+
 ##### `replace_all`
 
 Replaces a regular expression pattern in field values with a replacement string. Regexp capturing is possible; refer to capturing groups by number (`$<number>`) or name (`${<name>}`).
@@ -632,6 +680,8 @@ Replaces a regular expression pattern in field values with a replacement string.
 replace_all("<sourceField>", "<regexp>", "<replacement>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=replace+all)
+
 ##### `reverse`
 
 Reverses the character order of a string or the element order of an array.
@@ -650,6 +700,8 @@ sort_field("<sourceField>", reverse: "true")
 sort_field("<sourceField>", numeric: "true")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=sort+field)
+
 ##### `split_field`
 
 Splits a string into an array and replaces the field value with this array.
@@ -658,6 +710,8 @@ Splits a string into an array and replaces the field value with this array.
 split_field("<sourceField>", "<separator>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=split+field)
+
 ##### `substring`
 
 Replaces a string with its substring as defined by the start position (offset) and length.
@@ -695,6 +749,8 @@ Deletes whitespace at the beginning and the end of a field value.
 trim("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=trim)
+
 ##### `uniq`
 
 Deletes duplicate values in an array.
@@ -703,6 +759,9 @@ Deletes duplicate values in an array.
 uniq("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=uniq)
+
+
 ##### `upcase`
 
 Upcases all characters in a field value.
@@ -711,6 +770,8 @@ Upcases all characters in a field value.
 upcase("<sourceField>")
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=upcase)
+
 ##### `uri_encode`
 
 Encodes a field value as URI. Aka percent-encoding.
@@ -742,6 +803,8 @@ if <condition>
 end
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=reject)
+
 ### Binds
 
 #### `do list`
@@ -754,6 +817,8 @@ do list(path: "<sourceField>")
 end
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=do+list)
+
 Only the current element is accessible in this case (as the root element).
 
 When specifying a variable name for the current element, the record remains accessible as the root element and the current element is accessible through the variable name:
@@ -764,6 +829,8 @@ do list(path: "<sourceField>", "var": "<variableName>")
 end
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=do+list+with+var)
+
 #### `do list_as`
 
 Iterates over each _named_ element of an array (like [`do list`](#do-list) with a variable name). If multiple arrays are given, iterates over the _corresponding_ elements from each array (i.e., all elements with the same array index, skipping elements whose arrays have already been exhausted).
@@ -797,6 +864,8 @@ do once()
 end
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=do+once)
+
 In order to execute multiple blocks only once, tag them with unique identifiers:
 
 ```perl
@@ -833,6 +902,8 @@ end
 call_macro("<macroName>"[, <dynamicLocalVariables>...])
 ```
 
+[Playground-Example](https://metafacture.org/playground/?example=do+pu+macro)
+
 ### Conditionals
 
 Conditionals start with `if` in case of affirming the condition or `unless` rejecting the condition.