/usr/share/radare/gradare/Search/hex-pairs is in radare-gtk 1:1.5.2-6.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 | #!/bin/sh
eval `rsc EntryDialog "Search hex-pair" "Search string hex-pair formatted"`
[ -n "$VARIABLE" ] && echo ":/x $VARIABLE"
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