print $f,$l,"\n";
#becomes one of:
{ local $, = ' '; print $f, $l; print "\n"; }
print $f, ' ', $l, "\n";
print join(' ', $f, $l), "\n";

##</code><code>##

print $f . $l . "\n";
# becomes
print $f . " " . $l . "\n";

##</code><code>##

print "$f$l\n";
# becomes
print "$f $l\n";

##</code><code>##

printf "%s%s\n", $f, $l;
# becomes
printf "%s %s\n", $f, $l;