danilkolikov

# Detects binary number which is multiple of 3
# Example of subroutines in regexps

while (<>) {
    print if /
        (?(DEFINE)
            (?'A' (?:0(?P>F))? | (?:1(?P>B))? )
        )
        (?(DEFINE)
            (?'B' (?:1(?P>A)) | (?:0(?P>C)) )