It happens quite often that directories contain files names which are tailored according to some rule, like a common generic part. The following script demonstrates how the names of these files can be changed.
#!/usr/bin/perl -w
#
# searches the current directory for files that are named '*_fzm.fio' and
# renames them to '*_online.fio'.
#
use strict;
my $temp;
my @files = <*_kzm.fio>;
foreach my $file (@files)
{
$temp = $file;
$temp =~ s/_kzm\.fio/_online\.fio/;
print " renaming $file to $temp \n";
system( "mv $file $temp");
}