grep: retire study()

[mknos]

• Current perl treats study() call as no-op so delete it [1]
• grep was the only caller of study(); no other scripts need updating
• While here, convert a "use" statement within a condition to a "require" (found by perlcritic)
• Regression test: "perl grep -Hn include a.c b.c" --> still highlights the matching part of each line on my Linux system

1. https://perldoc.perl.org/functions/study

[coveralls]

Pull Request Test Coverage Report for Build 10957973451

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 73.069%

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Totals
Change from base Build 10953975344:	-0.7%
Covered Lines:	350
Relevant Lines:	479

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💛 - Coveralls