use strict;
use warnings;

my @pairs = (
    ['WORKING -STORAGE SECTION.', 'declare'],
    ['PROGRAM -BEGIN.', 'begin;'],
    ['^DISPLAY', 'PUT'],
    ['^ACCEPT', 'GET'],
    ['PROGRAM -DONE.', 'END;'],
    );

open sourcefile, '<', "source.cbl" or die "Can't open: $!";
open targetfile, '>', "source.ada" or die "Can't open: $!";

while (defined (my $line = <sourcefile>)) {
    $line =~ s/$_-[0]/$_->[1]/ for @pairs;
    print targetfile $line;
}