How can I make a regex apply to each line of a file?

Kage has asked for the wisdom of the Perl Monks concerning the following question:

ok... if I did like

open (FILE,"<$footer");
if ($lock){ flock(DATA, $lock)}
@footerfile = <FILE>;
close(FILE);
foreach $footerline(@footerfile) {
print "$footerline";
}
[download]

how would I put in a while( $tmpl = <FILE> ) { $tmpl =~ s/<<whatever>>/$whatever/g; } ?

Edit kudra, 2001-10-30 Changed title

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