Support Perl 5.42

[kfly8]

Summary

• Add Perl 5.38, 5.40, 5.42 to the GitHub Actions test matrix
• Update actions/checkout from v2 to v4

Test plan

• Verify GitHub Actions workflow runs successfully with Perl 5.38
• Verify GitHub Actions workflow runs successfully with Perl 5.40
• Verify GitHub Actions workflow runs successfully with Perl 5.42

Closes #30

🤖 Generated with Claude Code

[coveralls]

Pull Request Test Coverage Report for Build 20565655842

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 4523021970:	0.0%
Covered Lines:	84
Relevant Lines:	84

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💛 - Coveralls