use strict;
use warnings;
open "SOURCEFILE", '<', "source.cbl" or die "Can't open: $!";
open "TARGETFILE", '>', "source.ada" or die "Can't open: $!";

while (defined (my $line = <SOURCEFILE>)) {
    if ($line =~ s/WORKING -STORAGE SECTION\./declare/) 
    {
        print TARGETFILE $line;
    } 
    elsif ($line =~ s/PROGRAM -BEGIN\./begin/)
    {
        print TARGETFILE $line;
    }
    elsif ($line =~ s/DISPLAY/PUT/) 
    {
        print TARGETFILE $line;
    } 
    elsif ($line =~ s/ACCEPT/GET/) 
    {
        print TARGETFILE $line;
    }
    elsif ($line =~ s/PROGRAM -DONE\./END;/) 
    {
        print TARGETFILE $line;
    } 

}

close SOURCEFILE or die "Can't close: $!";
close TARGETFILE or die "Can't close: $!";