Assuming you don't want to implement a regular expression interpreter, then I'd bet your code is fairly close to optimal. You could simplify your test to 
use strict;
use warnings;

for ('a*', '*') {
    print validate($_) ? "Pass: '$_'\n" : "Fail: '$_'\n";
}

sub validate{
    my $pat = shift;
    return eval{qr/$pat/};
}

[download]
where it returns the compiled regular expression if it succeeds (TRUE) or undef if it fails (FALSE). (In general IMHO, it's a good idea to just return; on failure, since return 0; will evaluate to TRUE in list context. will return a non-empty list if the sub is evaluated in list context)

Blah blah, security, blah blah, trusted source, blah blah, injection attack, blah blah, perlsec.

Update: In deference to ikegami's comment, I have revised the above; however I would point out that Perl Best Practices agrees with me (point 124 - Use a bare return to return failure). I think we can both agree that the interface you specify should depend on how you are going to use it.

In reply to Re: Validating Regular Expression by kennethk
in thread Validating Regular Expression by Anonymous Monk

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