if (X) { ... } else { ... }

##</code><code>##

if (X) { ... } if (not X) { ... }

##</code><code>##

unless (X) { ... } else { ... }
if (not X) { ... } if (not not X) { ... }

##</code><code>##

print ... unless $quiet; # I want to print.
exit if $done;           # I might want to exit here.
exit unless $stay;       # I want to exit here, but apparently
                         # something is holding me back.