In "Windows Powershell in Action", Bruce Payette (one of the co-designers of Powershell) states:

"NOTE PowerShell uses the at symbol (@) in a few places, has $_ as a default variable, and uses & as the function call operator. These elements lead people to say that PowerShell looks like Perl."

"In practice, at one point, we did use Perl as a root language, and these elements stem from that period. Later on, the syntax was changed to align more with C#, but we kept these elements because they worked well. In Perl terminology, they contributed significantly to the 'whipupitude quotient' of the language."