filter Find-Function
{
   $path = $_.FullName
   $lastwrite = $_.LastWriteTime
   $text = Get-Content -Path $path
   
   if ($text.Length -gt 0)
   {
      
      $token = $null
      $errors = $null
      $ast = [System.Management.Automation.Language.Parser]::ParseInput($text, [ref] $token, [ref] $errors)
      $ast.FindAll({ $args[0] -is [System.Management.Automation.Language.FunctionDefinitionAst] }, $true) |
      Select-Object -Property Name, Path, LastWriteTime |
      ForEach-Object {
         $_.Path = $path
         $_.LastWriteTime = $lastwrite
         $_
      }
   }
}

PS> dir $home -Filter *.ps1 -Recurse -Exclude *.ps1xml | Find-Function
Name                       Path                       LastWriteTime          
----                       ----                       -------------          
Inject-LogonCredentials    C:\Users\Tobias\Desktop... 06.01.2014 02:43:00    
Test-Command               C:\Users\Tobias\Desktop... 06.03.2014 10:17:02    
Test                       C:\Users\Tobias\Desktop... 30.01.2014 09:32:20    
Get-WebPictureOriginal     C:\Users\Tobias\Desktop... 11.12.2013 11:37:53    
Get-ConnectionString       C:\Users\Tobias\Documen... 23.05.2014 10:49:09    
Convert-SID2User           C:\Users\Tobias\Documen... 23.05.2014 15:33:06    
Lock-Screen                C:\Users\Tobias\Documen... 19.03.2014 12:51:54    
Show-OpenFileDialog        C:\Users\Tobias\Documen... 16.05.2014 13:42:16    
Show-UniversalData         C:\Users\Tobias\Documen... 16.05.2014 13:23:20    
Start-TimebombMemory       C:\Users\Tobias\Documen... 23.05.2014 09:12:28    
Stop-TimebombMemory        C:\Users\Tobias\Documen... 23.05.2014 09:12:28    
(...)