use strict;
my $str = '["Text1;Text2;....;TextN"];asjkdjksd;ajksdjksad["Text1;Text2;....;TextN"]
.["Text1;Text2"]...long text...["Text1;Text2;Text3"]....long text...["Text1;...;TextN"]...long text...
I ONLY want to change the ";" in the ["Text1;...;TextN"]';
my $regex = qr/;(?=[^[]*])/mp;
my $subst = ',';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html