regexperlbraces

Perl Regex match balanced parentheses

Following strings - match:

"MNO(A=(B=C) D=(E=F)) PQR(X=(G=H) I=(J=(K=L)))" - "MNO"
"MNO(A=(B=C) D=(E=F))" - "MNO"
"MNO" - "MNO"
"RAX.MNO(A=(B=C) D=(E=F)) PQR(X=(G=H) I=(J=(K=L)))" - "RAX.MNO"
"RAX.MNO(A=(B=C) D=(E=F))" - "RAX.MNO"
"RAX.MNO" - "RAX.MNO"

Inside every brace, there can be unlimited groups of them, but they have to be closed properly.

Any ideas? Don't know how to test properly for closure.

I have to use a Perl-Regular-Expression.

Solution

  • In Perl or PHP, for example, you could use a regex like

    /\((?:[^()]++|(?R))*\)/

    to match balanced parentheses and their contents.

    See it on regex101.

    To remove all those matches from a string $subject in Perl, you could use

    $subject =~ s/\((?:[^()]++|(?R))*\)//g;

    Explanation: 

    \(       # Match a (
(?:      # Start of non-capturing group:
 [^()]++ # Either match one or more characters except (), don't backtrack 
|        # or
 (?R)    # Match the entire regex again, recursively
)*       # Any number of times
\)       # Match a )