Use the aliasing feature of for

for ($busi1, $busi2, $busi3) {
    s/-//g;
}
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I.e., the indidual items you loop over are being aliased to $_ in this case.

Or use an array instead of individual variables named $var1, $var2, ..., in which case the above would reduce to

for (@busi) {
    s/-//g;
}
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(But naturally, when you want to refer to a single value only in other places of your code, you'd then have to say, for example, $busi[2])