URLDecode changes each %XX encoding in s back into a single character. Each plus (+) is changed into a space.

$\mathrm{HTTP}:-\mathrm{URLDecode}\left(''Hello+World\%21''\right)$

$''Hello\; World!''$

The HTTP[URLDecode] command was introduced in Maple 15.

For more information on Maple 15 changes, see Updates in Maple 15.