use warnings;
use strict;

while (1) {
    system("clear");
    print "Enter P to process a file or Q to quit: ";
    chomp( my $ans=<STDIN> );

    if ( $ans =~ /^p$/i ) {
        print "What file would you look to open? ";
        chomp( my $file=<STDIN> );
        next if !-e $file;
        open(my $fh, '<', $file) or die "Could not open file: $!";

        print "What text would you like to search for? ";
        chomp( my $find=<STDIN> );

        print "What text would you like it replaced with? ";
        chomp( my $replace=<STDIN> );

        while ( my $line=<$fh> ) {
            if ( $line =~ /$find/i ) {
                $line =~ s/\b$find\b/$replace/g;
            }
            print $line;
        }
        next;
    }
    elsif ( $ans =~ /^q$/ ) {
        exit;
    }
    else {
        next;
    }
}