Use of uninitialized value in perl - regex

Question

So I have this code:
use warnings;
use strict;
my #arr = ("stuff (06:13)", "more stuff (02:59)", "extra stuff (00:00)");
my #new_arr = map { /\((\d+:\d+)\)/ ; $1 } #arr;
my ( $sum, $hrs, $mins );
$sum = 0;
for my $t (#new_arr) {
my ( $h, $m ) = split m/:/, $t;
my $hm = $h * 3600;
my $tm = $m * 60;
$sum = $sum + $hm + $tm;
}
$mins = sprintf( "%02d", ( $sum % 3600 ) / 60 );
$hrs = int( $sum / 3600 );
print "$hrs:$mins\n";
and I got uninitialized value error
Use of uninitialized value $t in split at DR/Hello World/test.pl line 14.
Use of uninitialized value $h in multiplication (*) at DR/test.pl line 16.
Use of uninitialized value $m in multiplication (*) at DR/test.pl line 17.
so how can I fix that?

Answer 1

stuff (3+06:13) doesn't match /\((\d+:\d+)\)/, so $1 is left untouched, so $1 contains undef, so undef ends up in #arr.
It's unwise to use $1 without making sure the pattern matches. Either adjust the pattern to make sure it always matches,
/\(([\d+]+:\d+)\)/
Or filter out the results that don't match.
my #new_arr = map { /\((\d+:\d+)\)/ ? $1 : () } #arr;
-or-
my #new_arr = map { /\((\d+:\d+)\)/ } #arr;
You have a similar problem with map { /\((\d+\++)/ ; $1 }.

Answer 2

You're missing a capture in two of your regexes.
Your first one:
my #new_arr = map { /\((\d+:\d+)\)/ ; $1 } #arr;
Misses a capture in the first instance:
$VAR2 = [
undef,
'02:59',
'00:00'
];
Which can be corrected (see below).
Your second capture also fails to capture anything:
my #x = map {/\((\d+\++)/ ; $1 } #arr;
See:
$VAR3 = [
'3+',
undef,
undef
];
This is because your asking it to find a digit \d followed by a literal + one or more times, which only occurs in $arr[0]. Below i've adjusted to capture 0 if no capture is found:
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
my #arr = ("stuff (3+06:13)", "more stuff (02:59)", "extra stuff (00:00)");
my #new_arr = map { /\(.*?(\d+:\d+)\)/ ; $1 } #arr;
my #x = map {/\((\d+\+)|(0)/ ; $1 // $2 } #arr;
my ( $sum, $hrs, $mins );
$sum = 0;
for my $t (#new_arr) {
my ( $h, $m ) = split m/:/, $t;
my $hm = $h * 3600;
my $tm = $m * 60;
$sum = $sum + $hm + $tm;
}
$mins = sprintf( "%02d", ( $sum % 3600 ) / 60 );
$hrs = int( $sum / 3600 );
print "$hrs:$mins\n";
print Dumper (\#arr, \#new_arr, \#x);
$VAR1 = [
'stuff (3+06:13)',
'more stuff (02:59)',
'extra stuff (00:00)'
];
$VAR2 = [
'06:13',
'02:59',
'00:00'
];
$VAR3 = [
'3+',
'0',
'0'
];
Output:
9:12