Minor refactoring of code around expressions

[mr0re1]

• Remove unused ResolveGlobalVariables;
• Compile regexes once and remove exessive error handling;

Submission Checklist

• Have you installed and run this change against pre-commit? (pre-commit install)
• Are all tests passing? (make tests)
• Have you written unit tests to cover this change?
• Is unit test coverage still above 80%?
• Have you updated all applicable documentation?
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[tpdownes]

LGTM. The way I understand this change is that if (somehow) any of the regular expressions fail to compile, it will manifest as an immediate panic upon invoking ghpc with any set of arguments.

if I misunderstand, please let me know before merging.

[mr0re1]

if any of the regular expressions fail to compile, it will manifest as an immediate panic upon invoking ghpc

Correct. https://go.dev/play/p/3t2TrJmyJNL