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Though you might be able to parse this with a fancy regex, a simple state machine would in my opinion be easier to read and less complicated to write and debug. If I understand your post correctly, your string has four tokens:
  • quoted strings - opaque between the quotes
  • runs of non-whitespace/non-close parenthesis that begin with anything but an open parenthesis or double quote, /[^)("][^)\s]*/.
  • runs of whitespace used as a separator between the first two types of tokens
  • parenthesized strings that may contain any of the first three types of tokens.

Assuming there are no parenthesized tokens within parenthesized tokens, you could use something like this:

use strict; use warnings; while (my $line = <DATA>) { chomp $line; # store tokens other than separators my @aTokens; # state: are we inside or outside of a parenthesized token? my $bParen; my $sInParens=''; while ($line =~ /("[^"]+"|\(|\)|[^)\s]+|\s+)/g) { my $sToken = $1; if ($sToken eq '(') { #starting a parenthesized token $bParen=1; } elsif ($sToken eq ')') { #ending a parenthesized token: add it to the list $bParen=0; push @aTokens, "($sInParens)"; $sInParens=''; } elsif ($bParen) { # in the middle of a parenthesized token $sInParens .= $sToken; } elsif ($sToken =~ /^\S/) { # not a parenthesized token # either a quoted or unquoted non-whitespace token # add it to the list push @aTokens, $sToken; } } local $"='> <'; printf "input : %s\n%s", "<$line>", "tokens: <@aTokens>"; } __DATA__ xxx "()" ("charset" "ISO-8859-1") (")") "xxx"

If you also need parenthesized tokens within parenthesized tokens, they the loop is only slightly more complicated. You would need to change the flag $bParen to a counter that was incremented for each '(' and decremented for each ')' found. You would then build the token until $iParenCount returned to 0. Parentheses within quotes will have no effect on this count because the "[^"] run insures that only parentheses outside of quotes will get parsed into separate tokens:

use strict; use warnings; while (my $line = <DATA>) { chomp $line; my @aTokens; my $sInParens=''; my $iParenCount; while ($line =~ /("[^"]+"|\(|\)|[^)\s]*|\s+)/g) { my $sToken = $1; if ($sToken eq '(') { if ($iParenCount) { $sInParens .= $sToken; } $iParenCount++; } elsif ($sToken eq ')') { $iParenCount--; if ($iParenCount) { $sInParens .= $sToken; } else { push @aTokens, "($sInParens)"; $sInParens=''; } } elsif ($iParenCount) { $sInParens .= $sToken; } elsif ($sToken =~ /^\S/) { push @aTokens, $sToken; } } local $"='> <'; print "paren count: $iParenCount\n"; printf "input : %s\n%s", "<$line>", "tokens: <@aTokens>\n"; } __DATA__ xxx "()" ("charset" "ISO-8859-1") (")") "xxx" ((a)(b)(c)) yyy

Best, beth

Update: added some discussion about handling nested parenthesized tokens.

Update: Fixed overly greedy regex

In reply to Re: Extracting a parenthesized fragment from a string by ELISHEVA
in thread Extracting a parenthesized fragment from a string by fce2

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