/usr/bin/fslex is in fsharp 3.1.1.26+dfsg2-3.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | #!/bin/sh
EXEC="exec "
if test x"$1" = x--debug; then
   DEBUG=--debug
   shift
fi
if test x"$1" = x--gdb; then
   shift
   EXEC="gdb --eval-command=run --args "
fi
if test x"$1" = x--valgrind; then
  shift
  EXEC="valgrind $VALGRIND_OPTIONS"   
fi
# Beware this line must match the regular expression " (\/.*)\/fsi\.exe" when @TOOL@ is fsi.exe.
# That's because the FSharp MonoDevelop addin looks inside the text of this script to determine the installation
# location of the default FSharp install in order to find the FSharp compiler binaries (see 
# fsharpbinding/MonoDevelop.FSharpBinding/Services/CompilerLocationUtils.fs). That's a pretty unfortunate
# way of finding those binaries. And really should be changed.
SILLY_ENV_HACK_FOR_REGEX=mono $EXEC cli $DEBUG $MONO_OPTIONS /usr/lib/cli/fsharp/FsLex.exe "$@"
 |