use strict;
use warnings;

sub is_delimiter_balanced {
    my ($delimiter, $text) = @_;
    return
    (
    substr($text,0,1) =~ m|^[\Q$delimiter\E]| 
    and 
    $text =~ m/ \Q$delimiter\E [^\\$delimiter]* (\\.[^\\$delimiter]*)* \Q$delimiter\E /gcsx
    );
}

use Data::Dumper;
print "first:\n";
print Dumper(is_delimiter_balanced(q{'}, q{'a\'b'test}));
print "second:\n";
print Dumper(is_delimiter_balanced(q{'}, q{'a\'btest}));

输出：

first:
$VAR1 = '\\\'b';
second: