Or the FileHandle module even
Update: changed vars to more descriptive names

#!/usr/bin/perl

use strict;
use FileHandle;

# what to watch
my %monitor = (
   'messages' => '/var/adm/messages',
);

# how to watch it.
my %handles;
for ( keys %monitor ) {
   $handles{ monitor{$_} } = new FileHandle "$monitor{$_}", "r"
      or die "Cant open $monitor{$_}: $!\n";
}


# And use it 
# WARNING blocking code ahead!!
my $sentinel; # how we get out of the while 1
while (1) {
   last if $sentinel;

   while ( my($file, $fh) = each %handles ) {
      chomp(my $line = <$fh>);
      print "Saw in file: $file\n$line\n\n";
   
      $sentinel++ if $line =~ m/somethingorother/;
   } 
}
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Also File::Tail might be of some use along the same lines