#!/usr/bin/perl
foreach my $file (glob "lab1*") {
  my $newfile = $file;
  $newfile =~ s/\.FIT/\.fits/;
  if (-e $newfile) {
    warn "can't rename $file to $newfile: $newfile exists\n";
    } elsif (rename $file, $newfile) {
      ## success, do nothing
    } else {
      warn "rename $file to $newfile failed: $!\n";
    }
}