They are compared when you say

use Some::Module 6.41;
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See use for documentation, especially

If the VERSION argument is present between Module and LIST, then the use will call the VERSION method in class Module with the given version as an argument:

        use Module 12.34;
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is equivalent to:

        BEGIN { require Module; Module->VERSION(12.34) }
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The default VERSION method, inherited from the UNIVERSAL class, croaks if the given version is larger than the value of the variable $Module::VERSION .

> Also, when is the thumb rule for creating new versions?

See Semantic Versioning for one of the possible strategies.

> If I fix a typo in a comment, should I increment the version number?

Of course. CPAN/PAUSE would reject an upload with an existing version.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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