+ # Thanks to Rado in #awk on Freenode (2010-03-29 01:34) for the END tip to
+ # also work with empty stdin, and to prince_jammys in #awk on Freenode
+ # (2010-03-29 02:20) for a shorter syntax for "$0 !~".
+ which $1 2>&1 | awk '{ if (!/^\//) exit 1 }
+ END { if (NR == 0) exit 1 }'