If you use the special null filehandle for reading multiple files on the command line (i.e. if you read via <>) , the name of the current input file will show up in the special variable $ARGV (see perlvar). You can use this variable to determine whether the file name has changed because the next file has been opened, and (re-)open the output filehandle to another file. Of course you have to provide means to change the output file name (e.g. a prefix or suffix applied to the input file name, or a counter), otherwise the same file will be re-opened and clobbered.

Example:

my $filename; # used to remember the current file name
my $out = "output"; # prefix for output files
my $ofh; # output filehandle, currently closed
while (<>) {
    if ($ARGV ne $filename) {
        $filename = $ARGV;
        open $ofh, '>', "$out-$filename"
            or die "Can't write to '$out-$filename': $!\n";
    }
    print $ofh $_;
}

[download]
perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'

In reply to Re: reading files to different output files. by shmem
in thread reading files to different output files. by ic23oluk

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