Freeswitch ESL: regex

Evaluate a regex (regular expression).

Usage:

       regex <data>|<pattern>[|<subst string>][|(n|b)]
       regex m:/<data>/<pattern>[/<subst string>][/(n|b)]
       regex m:~<data>~<pattern>[~<subst string>][~(n|b)]

This command behaves differently depending upon whether or not a substitution string and optional flag is supplied:

If a subst is not supplied, regex returns either «true» if the pattern finds a match or «false» if not.
If a subst is supplied, regex returns the subst value on a true condition.
If a subst is supplied, on a false (no pattern match) condition regex returns: the source string with no flag; with the n flag regex returns null which forces the response «-ERR no reply» from regex;
with the b flag regex returns «false»
The regex delimiter defaults to the | (pipe) character. The delimiter may be changed to ~ (tilde) or / (forward slash) by prefixing the regex with m:

Examples:

regex test1234|\d                  <== Returns "true"
regex m:/test1234/\d               <== Returns "true"
regex m:~test1234~\d               <== Returns "true"
regex test|\d                      <== Returns "false"
regex test1234|(\d+)|$1            <== Returns "1234"
regex sip:foo@bar.baz|^sip:(.*)|$1 <== Returns "foo@bar.baz"
regex testingonetwo|(\d+)|$1       <== Returns "testingonetwo" (no match)
regex m:~30~/^(10|20|40)$/~$1      <== Returns "30" (no match)
regex m:~30~/^(10|20|40)$/~$1~n    <== Returns "-ERR no reply" (no match)
regex m:~30~/^(10|20|40)$/~$1~b    <== Returns "false" (no match)
Logic in revision 14727 if the source string matches the result then the condition was false however there was a match and it is 1001.

regex 1001|/(^\d{4}$)/|$1

https://freeswitch.org/confluence/display/FREESWITCH/Regular+Expression