Tcl is historically very slow. Especially for synthetic CPU intensive benchmarks. However, since it's so easy to interop with C, it didn't seem to matter much in the real world. You just put anything performance sensitive in C and left the bits that didn't matter in tcl. Some benchmarks: https://github.com/trizen/language-benchmarks
http://mcvoy.com/lm/L/tcl/tests/langbench/
some results in the README. Perl holds up well. These are probably 10 years old though.