Perl | pos() function in Regular Expression

pos() function in Perl is used to return the position of the last match using the 'm' modifier in Regex. 
pos function can be used with the character classes in Regex to return a list of all the required substring positions in the given string. Global operator 'g' can also be used along with the 'm' modifier to search for the substring within the whole text.
 

Syntax: pos(String) 
Parameter: String after applying Regular Expression 
Returns: the position of the matched substring 
 

Example 1: Using a substring character 
 

Position of 'G' in string:
1
11

 
Example 2: Using a character class 
 

Position of all Uppercase characters:
1, 7, 11, 
Position of all Lowercase characters:
2, 3, 4, 5, 8, 9, 12, 13, 14, 15,

 
Example 3: Position of spaces 
 

6
10

  
Use of \G Assertion to match from specified position:
\G Assertion in Perl Regex is used to match the substring starting from a position specified by pos() function till the matching character specified in the regex. This will return the position of the first occurrence of the character specified by the 'm' modifier. 
Example: 
 

8 rld is the best

In the above example, the position of the first occurrence of the matching substring is printed along with the remaining string. If there is a need to restart counting position for the next occurrence of the matching character, just store the remaining string that is in $1, into the default string.
Example: 
 

8 rld is the best among all
19 ng all