use strict;
use warnings;

my $seconds;

# 1) min:sec,frac  e.g. "5:29,11"
# 2) sec,frac      e.g. "29,11"
# 3) sec           e.g. "29"
# 4) ,frac         e.g. ",11"
# 5) min:sec       e.g. "5:29"
# 6) someth. else  e.g. "abc"


my $time = " 5:21,11 ";

# remove leading and trailing whitespace characters
$time =~ s/^\s+|\s+$//g;

if( $time =~ m/[^0-9:,]+/ )
{
    $seconds = -1;
}
elsif( $time =~ m/((?<min>\d+):)?
               ((?<sec>\d+))?
               (,(?<frac>\d+))?/x )
{
    $seconds = ($+{'min'} * 60) + $+{'sec'} + ($+{'frac'}/(10**length($+{'frac'})));    
}

print("$seconds\n");