in response to https://lists.macosforge.org/pipermail/macports-dev/2014-September/028190.html

variants.sed

# Save port to hold space.
/ has the variants/ {
    s/ has .*$//
    h
    d
}

# Remove noise.
/conflicts with/d
/^[^:]*mariadb[^:]*:/b db_variant
/^[^:]*mysql[^:]*:/b db_variant
/^[^:]*percona[^:]*:/b db_variant
d

:db_variant

# Append desired suffix to variant name.
/^\[+\]/s/.*]\(.*\):.*$/\1	Default/
/^[[:blank:]]*+/s/[[:blank:]]*+\(.*\):.*$/\1	Y/
/^[[:blank:]]*[^+]/s/[[:blank:]]*\(.*\):.*$/\1	N/

# Extract port name from hold space and append variant name and suffix.
x
s/[[:blank:]].*$//
G
s/\n/	/

# Print pattern space and save to hold space for subsequent lines.
p
h