Fix unit tests on test_interperter doing startswith(...) != -1

[orpuente-MS]

Closes #1723

[github-actions]

Benchmark for 5193e6a

Click to view benchmark

Test	Base	PR	%
Array append evaluation	331.9±2.55µs	331.6±2.81µs	-0.09%
Array literal evaluation	169.8±6.10µs	172.3±4.20µs	+1.47%
Array update evaluation	408.2±1.01µs	409.6±2.71µs	+0.34%
Core + Standard library compilation	23.9±0.78ms	22.1±0.48ms	-7.53%
Deutsch-Jozsa evaluation	4.8±0.04ms	4.8±0.05ms	0.00%
Large file parity evaluation	34.3±0.29ms	34.2±0.15ms	-0.29%
Large input file compilation	13.3±0.26ms	12.8±0.23ms	-3.76%
Large input file compilation (interpreter)	52.8±1.03ms	51.1±1.31ms	-3.22%
Large nested iteration	32.1±0.25ms	32.0±0.15ms	-0.31%
Perform Runtime Capabilities Analysis (RCA) on Deutsch-Jozsa sample	1597.3±92.81µs	1591.1±138.97µs	-0.39%
Perform Runtime Capabilities Analysis (RCA) on large file sample	8.1±0.14ms	8.1±0.23ms	0.00%
Perform Runtime Capabilities Analysis (RCA) on teleport sample	1453.0±105.15µs	1419.7±36.64µs	-2.29%
Perform Runtime Capabilities Analysis (RCA) on the core and std libraries	28.4±0.76ms	28.2±0.71ms	-0.70%
Teleport evaluation	89.4±3.43µs	90.9±7.78µs	+1.68%