Source code in the n/t/roff programming language

.nr BS 99 1
.de L1
.ie \\n(BS>1 \{ \
\\n(BS bottles of beer on the wall,
\\n(BS bottles of beer.\c
\}
.el \{ \
\\n(BS bottle of beer on the wall,
\\n(BS bottle of beer.\c
\}
Take one down, pass it around,
\\n-(BS bottles of beer on the wall.

.if \\n(BS>0 .L1
..
.nf
.L1
.fi

.nr beers 99 1
.nf
.while \n[beers]>0 \{ \
.ie \n[beers]>1 \{ \
\n[beers] bottles of beer on the wall,
\n[beers] bottles of beer.\c
\} \" ie \n[beers]>1
.el \{ \
\n[beers] bottle of beer on the wall,
\n[beers] bottle of beer.\c
\} \" el
Take one down, pass it around,
\n-[beers] bottles of beer on the wall.
\} \" while \n[beers]>0
.fi