Weird Regexes Stuff

slinky773 has asked for the wisdom of the Perl Monks concerning the following question:

I was going through Sam's Teach Yourself Perl in 24 hours and I got to the end of hour 6, the regex section, and I see this activity:

See whether you can produce a pattern to match a standard time format.
+ All
the following should be acceptable: 12:00am, 5:00pm, 8:30AM. These sho
+uld probably not be accepted: 3:00,2:60am, 99:00am, 3:0pm.
[download]

OK, easy enough:

#!/usr/bin/perl -w
use strict;
use warnings;

print "Type in the current time!\n";

my $input = <STDIN>;

while($input)
{
    if($input =~ m/(\d)*(\d):(\d)(\d)(\w)(\w)/ | $input =~ m/(\d)*(\d)
+:(\d)(\d)(\s)(\w)(\w)/)
    {
        if($1 > 1 || $2 > 2 || $3 > 6)
        {
            print "That is not a valid time!\n";
            print "Type the time again.\n";
            
            $input = <STDIN>;
        }
        else
        {
            print "That is a valid time!\n";
            $input = 0;
        }
    }
    else
    {
        print "Please be more specific.\n";
        
        $input = <STDIN>;
    }
}
[download]

However, this is the terminal output:


Last login: Thu Aug 18 11:28:44 on ttys000
youngs-mac-mini:~ fenimore$ cd ~/Documents
youngs-mac-mini:Documents fenimore$ perl TimeChecker.pl
Type in the current time!
4:90
Please be more specific.
4:30AM
Use of uninitialized value $1 in numeric gt (>) at TimeChecker.pl line
+ 13, <STDIN> line 2.
That is not a valid time!
Type the time again.
12:30PM 
That is a valid time!
youngs-mac-mini:Documents fenimore$
[download]

Er... any help here? For added clarity, this is line 13:

        if($1 > 1 || $2 > 2 || $3 > 6)
[download]

Comment on Weird Regexes Stuff Select or Download Code

Replies are listed 'Best First'.
Re: Weird Regexes Stuff by toolic (Bishop) on Aug 18, 2011 at 17:08 UTC
(\d)(\d)* Try changing that to `(\d{1,2})` [download] but you'll then have to adjust your $1,$2,$3. See perlre	[reply] [d/l]
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Re: Weird Regexes Stuff by Samy_rio (Vicar) on Aug 18, 2011 at 18:00 UTC
Updated this may help you `#!/usr/bin/perl -w use strict; use warnings; my $input = 'All the following should be acceptable: 12:00am, 5:00pm, +8:30AM. These should probably not be accepted: 3:00,2:60am, 99:00am, +3:0pm, 29:00AM.'; while ($input =~ m/\W([1-9]\|[01][0-2]\|2[0-3]):[0-5][0-9][ap]m/gsi) { print "This is a valid time!\t$&\n"; } __END__ OUTPUT This is a valid time! 12:00am This is a valid time! 5:00pm This is a valid time! 8:30AM` [download] Regards, Velusamy R. eval"print uc\"\\c$_\""for split'','j)@,/6%@0%2,`e@3!-9v2)/@\|6%,53!-9@2~j';	[reply] [d/l] [select]
Re^2: Weird Regexes Stuff by AnomalousMonk (Archbishop) on Aug 18, 2011 at 18:11 UTC
`>perl -wMstrict -le "my $input = '12:00AM 29:00AM'; while ($input =~ m/\W(0\|[0-2]?[0-9]):[0-5][0-9][ap]m/gsi) { print qq{This is a valid time!\t'$&'}; } " This is a valid time! ' 29:00AM'` [download]	[reply] [d/l]
Re^2: Weird Regexes Stuff by AnomalousMonk (Archbishop) on Aug 19, 2011 at 07:47 UTC
The updated solution still has a problem, IMO, with that pesky `\W` anchoring the start of the match. Is the following really what you intend? `>perl -wMstrict -le "my $input = '12:00am, 5:00pm,8:30AM'; while ($input =~ m/\W([1-9]\|[01][0-2]\|2[0-3]):[0-5][0-9][ap]m/gsi) { print qq{This is a valid time!\t$&}; } " This is a valid time! 5:00pm This is a valid time! ,8:30AM` [download]	[reply] [d/l] [select]