use strict;
use warnings;

# We should end up with Flameless-Candles.htm Classic-Cars.htm Apricot
+-Jelly.htm 
# Where string ABC123 has been replaced with Flameless Candles in the 
+Flameless-Candles.htm file and ABC123 has been replaced with Classic 
+Cars in the Classic-Cars.htm file etc. 

while (my $phrase = <DATA>) {
    chomp ($phrase);
    my $filename = "$phrase.htm";
    $filename =~ s/\s+/-/g;
    
    if (open(my $infh, '<', $filename)) {
        if (open(my $outfh, '>', "$filename.out")) {
            while (<$infh>) {
                s/ABC123/$phrase/g;
                print $outfh $_
            }
            close $infh;
            close $outfh;
            rename "$filename.out",$filename or 
                warn "Unable to rename $filename.out: $!"
        }
        else {
            warn "Unable to open $filename.out: $!";
            close $infh;
        }
        
    }
    else {
        warn "Unable to open $filename: $!";
    }

}

__DATA__
Flameless Candles
Classic Cars
Apricot Jelly
[download]

Thank you, I am studying this.