\input mydefs.tex

\def\singlespace{}


\def\regexpexample{\(\catcode`\&=4\relax\doreexample}
\def\doreexample#1\crcr{\halign{\hskip 1in ##\quad\hfil&\rm ##\hfil\cr
#1\crcr}\)}

\message{fod\the\catcode`\&}

\regexpexample
`001122` =~ /`00 11 22`/&returns true,\cr
`001122` =~ /`00 11 22`/&returns true,\crcr

\(\catcode`\&=4
\doreexample `001122` =~ /`00 11 22`/&returns true,\crcr

\bye