My idea of solving this is putting the intervals into an array and then selecting the "right" bucket for the length. I assume that you can somehow get at the playlength of a file in seconds. (untested code follows):

my @playlengths = (
  0,
  1*60,
  2*60,
  3*60,
  4*60,
  5*60,        # this is just to show
 10*60,        # that we can have gaps in the array
 60*60,        # and anything longer than one hour
        # goes into this bucket ...
 2147483648,    # I use this as an easy end-of-array marker
);

# First we retrieve the playlength in seconds
# from the current file for later reference
my $playlength = &getPlaylength( $file{$pos});

# $slot will hold the position of our file 
# so @playlengths[$slot] <= $playlength < $playlengths[$slot+1]
# always holds
my $slot = 0;

while ($playlength < @playlengths[$slot]) {
  $slot++;
};

if ($slot == $#playlengths) {
  print "The file playlength is longer than $playlengths[$slot] second
+s.\n";
} elsif ($slot == 0) {
  print "The file playlength is below ",$playlengths[1]," seconds.\n";
} else {
 print "The file playlength is between $playlengths[$slot] and $playle
+ngths[$slot+1] seconds."
};
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